Devices Fabrication with Narrow-Bandgap a-SiGe:H Alloys Deposited by HWCVD

Yueqin Xu, Baojie Yan, Brent P. Nelson, Eugene Iwaniczko, Robert C. Reedy, A. H. Mahan, Howard Branz

Research output: Contribution to conferencePaperpeer-review

5 Scopus Citations


We incorporate narrow-gap amorphous silicon germanium (a-SiGe:H) alloys grown by hot-wire chemical vapor deposition (HWCVD) into single-junction n-i-p solar cells, and improve both fill factor (FF) and open-circuit voltage (V oc) by bandgap grading. The Taue bandgap (ET) of the a-SiGe:H is as low as about 1.25 eV. Previously [1], we obtained a short-circuit current density (Jsc) up to 20 mA/cm2 in an n-i-p device incorporating an ungraded 120-nm i-layer of 1.25-eV a-SiGe:H. However, without buffer layers or bandgap profiling, the fill factor was only 38%, likely due to an abrupt bandgap transition and poor hole collection. To overcome these problems, we have used composition bandgap profiling throughout the i-layer and improved both Voc and FF significantly without any Jsc loss. The solar cell efficiency is improved from 3.55% to 5.85% and Voc rises from 0.475 to 0.550 eV. This improved single-junction a-SiGe:H solar cell has a quantum efficiency of about 48% at λ=800 nm and about 15% at λ=900 nm. We present details of the bandgap profiling and its effect on device performance.

Original languageAmerican English
Number of pages6
StatePublished - 2004
EventAmorphous and Nanocrystalline Silicon Science and Technology - 2004 - San Francisco, CA, United States
Duration: 13 Apr 200416 Apr 2004


ConferenceAmorphous and Nanocrystalline Silicon Science and Technology - 2004
Country/TerritoryUnited States
CitySan Francisco, CA

NREL Publication Number

  • NREL/CP-520-36089


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